Bradley a



(No Model.)

B. A. FISKE. METHOD OF POINTING GUNS AT SEA.

Patented Sept. 9, 1890.

INVENTOI? ATTO/M'EY.

WITNESSES:

UNITED STATE-s PATENT OFFICE.

BRADLEY A. FISKE, OF THE UNITED STATES NAVY.

METHOD OF POINTING GUNS AT SEA.

SPECIFICATION forming part of Letters Patent No. 435,925, datedSeptember 9, 1890.

Application filed May 15, 1890. Serial No. 351,857. (No model.)

To aZZ whom it may concern:

Be it known that I, BRADLEY A. FISKE, of the United States Navy, haveinvented a new and useful Method of Pointing Guns at Sea, of which thefollowing is a specification.

My invention relates to a new method of pointing guns located upon avibrating, heeling, or rolling platform-such as a ship upon a distanttarget; and it consists (after determining the angle of elevation abovethe horizontal which it is necessary to give the gun in order to causethe projectile to traverse the given range) in adjusting a telescopemovable about a transverse axis approximately parallel to that of thegun at an angle to the axis of the bore of said gun equal to saidpredetermined angle of elevation, and then noting the moment when theline of sight of said telescope so adjusted intersects the target.

In the accompanying drawings, Figure 1 illustrates a vessel on an evenkeel, showing the vessels deck, the gun, and the telescope allhorizontal and parallel. Fig. 2 shows the vessel heeled over adeterminate angle, the gun still remaining parallel to the deck, but thetelescope disposed with reference to the deck over an angle equal tothat of the heel of the vessel. Fig. 3 shows the vessel heeled over adeterminate angle less than that shown in Fig. 2, the gun being elevatedabove the deck through the remaining part of that angle and thetelescope depressed over an angle equal to the heel of the vessel.

Similar letters of reference indicate like parts.

A represents a section of the hull of a ves sel, B O the water-line, andD E the line of the deck.

F is a gun mounted on the deck and capable of being elevated ordepressed, turning on its trunnions G.

H is a telescope or spy-glass supported on transverse pivots ort-runnions in any suit able way above the deck, and also capable ofbeing turned on vertical pivots so as to point at any object.

I11 Fig. l the vessel A is shown on an even keel, the deck-line D E,axis of the gun F, and axis of the spy-glass I-I all being parallel andhorizontal.

Let it be assumed that the gun is to fire at a target located at such adistance from the ship that the necessary elevation to be given to thegun above the horizontal would be (to illustrate) two degrees; butsuppose the ship heels over, as indicated in Fig. 2, so that thedeck-line makes an angle E I 0 equal to two degrees. Then, clearly, theaxis of the gun being parallel to the deck will make an angle of twodegrees with the horizontal, and thus by the rolling or heeling of theship the gun will be brought to the desired elevation. If it be thenfired,its projectile will (as assumed) traverse the distance to thetarget. The object of the telescope H is to determine the moment whenthe vessel in rolling or heeling reaches the point at which the gunattains the desired elevation. To this end, as soon as the extent ofelevation is determined, the telescope is set so that the angle betweenits axis and the axis of the gun shall equal this anglethatis, assuming,as before, the angle of elevation of the gun to be two degrees, theobject end of the telescope is depressed two degrees. (Full lines, Fig.2.) Therefore the angle between the line of sight of the tele scope andthe axis of the bore of the gun will be two degrees. The observer nowlooks through the telescope until he sees the crosshairs of thetelescope intersect the target, which may be assumed in all cases,without material error, to be located in a level line drawn from thetelescope. In order that the cross-hairs may intersect the target thevessel must heel or roll, so as to bring the telescope back to thehorizontal, or in the position indicated by the dotted lines, Fig. 2.When this happens, the gun is in the position shown, and hence at thedesired elevation. Suppose, however, that by reason of the smoothness ofthe sea the vessel does not roll or heel sufficiently to elevate the gunto the desired extent. Assuming this, as before, to be two degrees, letone degree be the maximum elevation producible by the heeling of thevessel. These conditions are illustrated in Fig. v3, the angle betweenthe deck-lineD E and the waterline B 0 being one degree. The gun is thenelevated on its trunnions over an angle of one degree, and inasmuch asthe angle between gun and telescope must equal that of the desiredelevation of gun, the telescope is depressed one degree, so that theangle between gun and telescope, as before,becomes two degrees.Therefore, when 5 the telescope is brought level by the heeling of theship and the target sighted through it the gun will stand at anelevation of two degrees above the horizontal-one degree being obtainedby the heeling of the vessel and one IO degree by the guns own elevationon its trunnions G. Of course the gun may be laid at any angle ofelevation and the telescope adjusted conformably.

The assumption made in the foregoing, that the line from the telescopeto the target floating' on the water is ahorizontal line, is strictlytrue only when the telescope points at a part of said target which is atthe same height above the water as the telescope itself; but underordinary conditions of practice this refinement may be neglected and thegun fired when the cross-hairs of the telescope cut any part of thetarget.

Among the advantages gained by my aforesaid method are that it does awaywith the use of all mechanical contrivances such as pendulums,spirit-levels, &o.-and allows the gun to be accurately adjusted inelevation with reference simply to the true horizontal line. It rendersunnecessary frequent adj ustment of the gun itself on its trunnions toeffect changes in elevation, the telescope being correspondinglydepressed instead. It places the determination of the instant of tiringthe gun in the control of a person distant 3 5 therefrom, and hence in aposition away from the excitement and hurry prevailing in the immediatevicinity of the gun; and finally, the piece can be sighted much moreaccurately by means of the telescope than is possio ble by the use ofthe rough sights on the gun itself.

I claim- The method of pointing a gun located on a rolling, heeling, orvibrating platform, which 5 consists in adjusting a telescope, alsolocated on said platform and movable on a transverse axis approximatelyparallel to that of the gun, at an angle to the axis of the bore of thesaid gun equal to a certain predetermined angle of elevation-necessaryto cause the projectile fired from said gun to travel to a given target,and, second, noting the moment when the line of sight of said adjustedtelescope is caused by the movement of said supporting-platform tointersect said target.

7 BRADLEY A. FISKE.

Witnesses:

M. BOSCH, PARK BENJAMIN.

